The present invention relates generally to disposable diapers and, more particularly, to a new and improved disposable absorbent diaper pad construction which provides improved pad integrity in use without adversely affecting pad flushability.
In recent years, improvements in disposable diapers have revolutionized the diapering of infants. As the term "disposable" implies, these diapers are designed to be discarded after a single use. Disposable diapers generally consist of an absorbent pad, a pad-covering topsheet which contacts the infant, and a liquid-impervious backsheet for containing liquid wastes within the absorbent pad. U.S. Pat. No. Re. 26,151 which issued to Duncan et al. on Jan. 31, 1967 is representative of such disposable diaper structures. As is taught by the Duncan et al. patent, a soiled diaper is preferably disposed of by stripping the moisture-impervious backsheet from the soiled absorbent portions of the structure prior to rinsing the soiled absorbent portions of the structure in a conventional toilet wherein it tends to disintegrate prior to flushing. When plies of creped cellulose wadding are employed as the absorbent media there is little or no need for enclosing the absorbent media within an envelope of wet strength tissue since the creped cellulose wadding generally has sufficient strength to provide satisfactory in use pad integrity. When, however, the absorbent media is comprised of a low-strength material such as air-laid wood pulp fluff, commonly referred to as airfelt, a strength-imparting envelope is generally necessary not only to provide satisfactory in use pad integrity, but also to avoid the dusting and linting problems commonly associated with such low-strength absorbent materials both during manufacture and in use. Failure to provide sufficient in use pad integrity in a disposable diaper adversely affects both its absorbency and its containment characteristics. Therefore a number of prior art disposable diaper structures have encapsulated the low strength absorbent media in an envelope of sheet material having at least some degree of wet strength, wet strength tissue paper being most commonly utilized. The chief disadvantage associated with such prior art structures, however, is that they do not disintegrate readily upon immersion in water unless the various layers of the structure are painstakingly disassembled by the user. Hence they are not readily flushable. The term "flushable" as used herein, is primarily intended to describe the ability of the absorbent media of a diaper pad structure to physically dissociate and structurally break down into small clumps of loose fibers by the normal action of rinsing the absorbent pad in water in an ordinary toilet bowl, without need for manually separating the various tissue layers employed in the absorbent pad of the diaper. All portions of the absorbent media should be capable of safely and harmlessly passing through a normal household sewage system without danger of clogging the system. Once the absorbent media has become dissociated from the portions of the diaper having at least some degree of wet strength, i.e., the topsheet and those portions of the tissue envelope which are immersed in the toilet bowl, the wet strength materials may either be flushed or wrapped within the moisture-impervious backsheet after rinsing for disposal in conventional solid waste disposal systems.
U.S. Pat. No. 3,636,952 which issued to George on Jan. 25, 1972 discloses a disposable diaper structure having an absorbent core comprised of airfelt contained within an envelope of cellulosic tissue, the various layers of the structure being secured together by means of embossing and gluing at their peripheries. The patent to George teaches that the diaper is preferably disposed of by stripping off and disposing of the moisture-impervious protective cover and then flushing the remainder of the structure in an ordinary toilet. However, as should be readily apparent from an inspection of the patent, the absorbent core material remains trapped between an envelope of cellulosic tissue paper after deposition in the toilet bowl and therefore the flushability of the structure is impaired unless the various layers of the structure are manually separated.
U.S. Pat. No. 3,586,000 which issued to Ness on June 22, 1971 likewise discloses a disposable diaper structure having a fluffed wood pulp absorbent filler encased on both sides by wet strength tissue. As with the patent to George, however, the absorbent media remains enclosed within an envelope of wet strength tissue upon stripping of the moisture-impervious backsheet prior to flushing.